••  irch  12,  1910. 


U.S.  DEPARTMENT   OF   AGRICULTURE, 

BUREAU   OF   ENTOMOLOGY-CIRCULAR  No.  120. 


L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


CONTROL  OF  THE  BROWN-ROT  AND  PLUM 
CURCULIO  ON  PEACHES. 


\Y.  M.  Scott,  of  tin  Bureau  of  Plant  Industry, 


A.  L.  (,h  uvi  \\i  i:.  ofth.  Bureau  of  Entomology. 


WASHINGTON   :  GOVERNMENT  PTINTINC  OFFICE    :    1910 


BUREAU  OF  ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  Chief  of  Bureau. 

C.  L.  Marlatt,  Assistant  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 
Chas.  J.  Gilliss,  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  insect  investigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

F.  M.  Webster,  in  charge  of  cereal  and  forage  insect  investigations. 

A.  L.  Quaintance,  in  charge  of deciduous  fruit  insect  investigations. 

E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  work. 
Rolla  P.  Currie,  in  charge  of  editorial  work. 

Mabel  Colcord,  librarian. 

[Cir.  120]  (2) 


Circular  No.  120.  Issued  March  i 

United  States  Department  of  Agriculture, 

BUREAU   OF   ENTOMOLOGY. 
L.  O.  HOWARD,   Entomologist  and  Chief  of  Bureau. 


CONTROL  OF   THK    BROWN-ROT   AND    PLUM   CURCULIO 

ON    PEACHES. 

By 

\Y.   M.  Scott,  of  tin  Bureau  of  Plant  Industry, 

and 
.'v.   L.  Qi  iintance,  oft)  Entomology. 

The  two  most  important  troubles  of  the  fruitofthe  peach  and  other 
stone  fruits  are  the  so  called  "brown-rot"  (Sclerotinia  fructigenia  (P.) 
Schrot.)  and  the  plum  curculio  ( I  bnotracht  lus  m  nuphar  I  lerbst  i.  The 
brown-rot  is  a  fungous  disease  of  the  flowers,  twigs,  and  fruit,  but  is 
especially  destructive  to  the  latter  as  it  approaches  maturity.  Dnder 
weather  conditions  favorable  to  the  fungus  from  one  half  to  three 
fourths  of  the  crop,  or  even  the  entire  crop,  maj  be  destroyed  within 
a  few  days.  The  marketed  fruit,  moreover,  rarely  reaches  its  desti 
nation  in  good  condition  and  is  often  a  disappointment  to  the  grower 
as  well  as  to  the  consumer.  This  destructive  disease  is  well  known  to 
peach  growers,  especially  in  the  Southern  States,  and  requires  but 
little  in  the  way  of  description.  Although  young  green  fruit  may 
become  infected,  it  is  the  ripening  fruit  which  suffers  most.  The 
disease  first  appears  as  a  ■-mall  brown  spot,  which  rapidly  enlarges 
involving  in  a  few  days  the  entire  fruit.  On  the  surface  of  the 
diseased  -pot-,  minute  tufts  of  spore  bearing  threads  appear,  giving 
to  the  fruit  a  grayish,  moldy  appearance. 

The  plum  curculio.  in  the  course  of  it-  feeding  and  egg  laying, 
punctures  the  fruit,  and  is  often  so  abundant  that  not  a. single  fruit 
escapes  injury.  The  puncture-  form  a  nidus  for  brown-rot  spores, 
greatly  favoring  infection.      Larva'  of  the  curculio.  hatching  from  the 

j-  placed  beneath  the  skin  of  the  peach,  make  their  way  to  the  pit. 
and  by  their  injury  cause  much  of  the  young  fruit  to  drop.  Fruit 
iufe-ted  later  in  the  season  may  ripen  prematurely  and  fall  or  lie  badly 
misshapen.  Wornainess  of  peaches  in  the  East  is  entirely  due  to  the 
plum  curculio,  and  the  injuries  of  this  insect  cause,  in  i he  aggregate, 
a  loss  each  year  to  fruit  growers  of  many  thousands  of  dollar-.      As 

[Cir.  120|  (3) 


4 

the  cuvculio,  by  its  punctures,  opens  the  way  for  brown-rot  infection 
of  peaches,  plums,  etc.,  its  control  becomes  doubly  important. 

While  the  curculio  is  not  of  itself  the  cause  of  brown-rot,  its  work 
very  great ly  favors  the  disease.  Furthermore,  it  is  practically  certain 
that  the  curculio  distributes  the  spores  of  the  fungus,  and  in  the  course 
of  its  feeding  and  egg  laying  actually  infects  the  fruit  with  the  fungus. 

As  is  well  known,  the  foliage  of  the  peach  and  other  stone  fruits  is 
especially  sensitive  to  sprays,  such  as  Paris  green  and  Bordeaux  mix- 
ture. This  has  largely  prevented  the  use  of  Bordeaux  mixture  and 
other  copper  compounds  for  the  control  of  peach  diseases.  While  it 
has  been  known  for  several  years  that  arsenate  of  lead  could  be  used 
in  the  treatment  for  curculio,  some  injury  has  resulted,  and  on  account 
of  the  well-known  sensitiveness  of  peach  foliage  entomologists  have 
been  cautious  about  recommending  it.  The  combination  treatment  for 
fungous  diseases  and  insect  enemies  so  successful  in  the  treatment  of 
the  apple,  grape,  etc.,  has,  therefore,  not  been  possible  on  the  peach. 

The  development  of  the  self -boiled  lime-sulphur  mixture,  however, 
as  a  fungicide  has  made  possible  the  control  of  the  brown-rot  and  some 
other  peach  diseases.  The  experiments  made  by  the  Bureau  of  Plant 
Industry,  with  the  self-boiled  lime-sulphur  mixture  on  the  peach,  cov- 
ering three  }'ears — from  1907  to  1909 — have  shown  conclusively  that 
when  properly  made  it  is  perfectly  harmless  to  the  foliage,  fruit,  and 
tender  growth  of  the  peach,  and  that  it  will  satisfactorily  control  brown- 
rot,  peach  scab,  and  other  fungous  diseases. 

In  experiments  conducted  during  the  past  season  it  was  found  that 
the  arsenate  of  lead  could  be  combined  with  the  self-boiled  lime-sulphur 
mixture  for  spraying  peaches,  and  that  this  insecticide  was  apparently 
less  injurious  in  the  combination  than  when  used  alone,  and  that  the 
combination  was  entirely  successful  in  controlling  the  seal),  brown- 
rot,  and  curculio.  The  addition  of  arsenate  of  lead,  as  shown  by  these 
and  other  experiments,  has  been  practically  without  injurious  effects 
where  not  more  than  two  applications  have  been  made.  Three  appli- 
cations, however,  of  an  arsenate-of-lead  spray  are  likely  to  cause 
shot-holing  of  the  leaves  and  an  excessive  reddening  of  the  fruit,  and 
under  certain  weather  conditions  such  symptoms  may  appear  as  the 
result  of  only  two  applications  of  the  poison,  though  ordinarily  not  to 
an  injurious  extent.  The  great  benefits  to  be  derived  from  spraying, 
it  is  believed,  will  much  more  than  offsel   any   possible  slight  injury. 

SOME    BES1  Lis   OF   SPRAYING." 

In  experiments  conducted  in  the  Hale  orchard,  at  Fort  Valley.  Ga., 
dining  1909,  by  the  Department  of  Agriculture,  the  practicability 
of    the   control    of     peach    scab,    brown-rot,   and    the   curculio    was 

o For  a  detailed  account  of  these  experiments,  see  Bulletin  174  of  the  Bureau  of 
Plant  Industry,  U.  S.  Department  of  Agriculture. 
[Cir.  120] 


thoroughly  demonstrated.  Thus  a  block  of  1,100  Elberta  trees  was 
sprayed,  first,  with  arsenate  of  lead  al  the  rate  of  2  pounds  to  50  gallons 
of  water  at  the  time  the  calyces,  or  shucks,  were  shedding;  second, 
with  '2  pounds  of  arsenate  of  lead  in  self-boiled  lime-sulphur  mixture 
(8  8  50)  three  weeks  later;  third,  with  self -boiled  lime  sulphur  mixture 
alone  a  month  later;  and,  fourth,  with  self-boiled  lime-sulphur  mix- 
ture a  month  In 'fort'  the  ripening  period  of  the  fruit.  At  picking  time 
95.5  per  cenl  of  t he  fruit  from  i he  sprayed  block  was  free  from  brown- 
rot,  93.5  per  cenl  free  from  scab,  and  72.5  per  cent,  free  from  the  cur- 
culio.  On  the  unsprayed  block  only  :'.T  percent  of  the  fruit  was  free 
from  brown-rot,  1  per  cent  free  from  scab,  and  2$  per  cent  free  from 
curculio  injury.  Inpackingthe  fruit  for  market  it  was  found  thai  the 
amount  of  merchantable  fruit  on  the  sprayed  block  was  ten  times  as 
great  as  from  the  unsprayed  block  containing  the  same  number  of 

tier-. 

( )n  a  block  of  Waddell  t  rees  spraj  ed  with  the  self-boiled  lime-sulphur 
mixture  alone,  one  month  after  the  falling  of  the  petals  and  again  one 
month  before  the  fruit  ripened,  the  results  were  not  quite  so  good, 
owing  to  curculio  infestation;  but  the  yield  of  merchantable  fruit 
was,  nevertheless,  LOO  per  cenl  more  than  thai  on  a  similar  block  of 
unsprayed  trees  of  the  same  variety. 

From  these  results  and  those  of  previous  experiments  we  may  con- 
clude that  the  peach  grower  now  has  at  his  command  a  reasonably 
safe  and  thoroughly  effective  remedy  for  the  peach  seal),  brown-rot, 
and  curculio.  By  carefully  following  the  instructions  given  below  he 
should  lie  able  effectively  to  prevent  these  troubles  at  a  small  cost. 

PREPARATION  OF  THE  SPRAY  MIXTURES. 

The  sprays  to  be  employed  are  the  self-boiled  lime-sulphur  mixture 
and  arsenate  of  lead.  The  arsenical  is  added  to  the  lime-sulphur  mix- 
ture, permitting  the  treal  ment  of  both  brown-rot  and.  the  plum  curculio 
at  one  and  the  same  time. 

'led  lime-sulphur  mixture. — This  mixture  is  composed  of  8 
pounds  of  fresh  stone  lime  and  8  pounds  of  sulphur  (either  flowers  or 
Hour  may  be  used)  to  50  gallons  of  water.  This  appears  to  be  about 
the  correel  strength,  although  in  mild  cases  of  scab  and  brown-rol  a 
weaker  mixture,  containing  6  pounds  of  each  ingredienl  to  50  gallons 
of  water,  may  be  used  with  satisfactory  resul  s.  The  mixture  can  best 
be  prepared  in  rather  large  quantities — say,  enough  for  200  gallons  al 
i  time,  making  the  formula  32  pounds  of  lime  and  32  pounds  of 
sulphur  to  be  cooked  with  a  small  quantity  of  water  (8  or  L0  gallons) 
and  then  diluted  to  200  gallons. 

The  lime  should  be  placed  in  a  barrel  and  enough  water  poured  on  to 
almost  cover  it.  As  soon  as  the  lime  begins  to  slake  the  sulphur 
should  be  added  after  first  running  it  through  a  sieve  t<>  break  up  the 

120] 


6 

lumps.  The  mixture  should  be  constantly  stirred  and  more  water 
added  as  needed  to  form  a  thick  paste  at  first  and  then  gradually  a 
thin  paste.  The  lime  will  supply  enough  heat  to  boil  the  mixture 
several  minutes.  As  soon  as  it  is  well  slaked  water  should  be  added 
to  cool  the  mixture  and  prevent  further  cooking.  It  is  then  ready  to 
be  strained  into  the  spray  tank,  diluted,  and  applied. 

The  stage  at  which  cold  water  should  be  poured  on  to  stop  the  cook- 
ing varies  with  different  limes.  Some  limes  are  so  sluggish  in  slaking 
that  it  is  difficult  to  obtain  enough  heat  from  them  to  cook  the  mix- 
ture at  all,  while  other  limes  become  intensely  hot  on  slaking  and  care 
must  be  taken  not  to  allow  the  boiling  to  proceed  too  far..  If  the 
mixture  is  allowed  to  remain  hot  fifteen  or  twenty  minutes  after  the 
slaking  is  completed,  the  sulphur  gradually  goes  into  solution,  com- 
bining with  the  lime  to  form  sulphids,  which  are  injurious  to  peach 
foliage.  It  is  therefore  very  important,  especially  with  hot  lime,  to 
cool  the  mixture  quickly  by  adding  a  few  buckets  of  water  as  soon  as 
the  lumps  of  lime  have  slaked  down.  The  intense  heat,  violent  boiling, 
and  constant  stirring  result  in  a  uniform  mixture  of  finely  divided 
sulphur  and  lime,  with  only  a  very  small  percentage  of  the  sulphur  in 
solution.  It  should  be  strained  to  take  out  the  coarse  particles  of 
lime,  but  the  sulphur  should  be  carefully  worked  through  the  strainer. 

Arsenate  of  lead.  Arsenate  of  lead  comes  on  the  market  in  a  thick, 
putty-like  paste,  and  must  be  worked  free  in  water  before  addition  to 
the  lime-sulphur  mixture.  There  are  several  brands  upon  the  market 
and  the  grower  should  be  careful  to  purchase  from  reliable  firms. 
The  addil  ion  of  arsenate  of  lead  to  the  self-boiled  lime-sulphur  mixture 
will  bring  about  a  decided  change  in  color,  but  without  injuriously 
affecting  the  value  of  the  spray.  Arsenate  of  lead  is  used  at  the  rate 
of  '1  pounds  to  each  50  gallons  of  water  or  lime-sulphur  mixture. 

The  amount  of  poison  required  for  each  spray  tank  of  mixture  may 
be  weighed  out  into  a  bucket,  thinned  with  water,  and  poured  through 
a  strainer  into  the  spra}^  tank.  In  extensive  operations,  however,  it 
is  much  more  convenient  to  prepare  a  stock  mixture  in  advance. 
Place  100  pounds  of  the  material  in  a  barn  1  with  a  bucket  of  water 
and  work  it  into  a  thin  paste  with  a  spade  or  a  large  paddle,  then 
dilute  with  water  to  *make  exactly  25  gallons.  When  thoroughly 
stirred,  each  gallon  will  contain  4  pounds  of  arsenate  of  lead,  and  the 
amount  of  poison  for  each  spray  tank  of  mixture  may  be  measured, 
thus  avoiding  the  trouble  of  weighing  small  lot-. 

SCHEDULE   OF   APPLICATIONS. 

For  the  Elberta,  Bell,  Reeves,  and  other  varieties  of  peaches  of 
about  the  same  ripening  season,  the  following  is  advised: 

First  application'.  —  About  the  time  the  calyces,  or  shucks,  are  shed- 
ding from  the  young  fruit,  spray  with  arsenide   of  lead  at  the  rate  of 

[Cir.  120] 


2  pounds  ti>  50  gallons  of  self  boiled  lime-sulphur  mixture.  Since  this 
application  is  rather  early  for  scab,  and  since  serious  outbreaks  of 
brow  11  rot  do  nol  usually  occur  a<  this  time,  the  self-boiled  mixture 
may  be  omitted  in  many  cases  with  reasonable  safety.  But  during 
warm,  rainy  springs,  especially  in  the  South,  the  lime-sulphur  mixture 
will  doubtless  be  necessary  in  this  application.  In  case  the  self-boiled 
lime-sulphur  mixture  is  nol  used  there  should  be  added  to  each  50 
gallons  of  water  the  milk  of  lime  made  from  slaking  2  or  •".  pounds  of 
good  -tone  lime,  in  order  to  counteract  any  can-tie  action  of  the  arse- 
nate of    lead. 

S  'ication.  — Two  or  three  u eeks  later,  <>r  about  one  monl h 

after  the  falling  of  the  petals,  spray  with  the  8  v--"''»  self-boiled  lime- 
sulphur  mixture  and  2  pounds  of  arsenate  of  lead. 

d  application.     About  one  month  before  the  fruit  ripens  spray 
with  the  8  s  50  self -boiled  liraeisulphur  mixture,  omitting  the  poison. 

For  earlier  maturing  varieties  of  peaches,  such  as  Waddell,  Car- 
man, and  llilev.  the  firsl  two  treatment-  outlined  above  will  usually 
be  sufficient,  but  in  ven  wet  seasons  badly  rotting  varieties  would 
probably  require  three  t  reatments.  Late  variet  ies,  such  as  Smock  and 
Salway.  having  a  longer  season,  would  not  he  thoroughly  protected  by 
three  applications,  hut  on  account  of  the  expense  there  i-  hesitation 
in  recommending  a  fourth  spraying.  In  view  of  the  results  obtained 
on  midseason  varieties,  ii  se<  ms  likely  that  three  treatments  will  ordi- 
narily lie  sufficient  for  the  late  varieties. 

APPLICATION    OF    rill.    SPRAT    MIXTURE. 

During  the  operation  of  spraying,  the  mixture  should  he  kept  well 
agitated.  <  >wing  to  the  tendency  of  t  he  -elf- hoi  led  lime-sulphur  mix- 
ture and  the  arsenate  Of  lead  to  settle  readily,  this  point  c;m  not  he 
too  strongly  emphasized.  If  the  spraying  outfit  is  not  equipped  with 
a  good  agitator,  the  spray  will  not  he  evenly  distributed,  with  the 
result  that  some  of  the  tree-  will  he  oversprayed  while  others  will 
receive  an  insufficient  application.  The  early  applications  of  spray 
should  he  made  rather  hea\  \  and  very  thoroughly  to  insure  the  de- 
struction of  the  curculio  and  protection  against  scab.  The  last  spray- 
ing, a  month  before  ripening  time  of  the  fruit,  should  he  made  with 
tine  nozzles,  the  object  being  t.>  give  the  fruit  a  uniform  coating  of  a 
mistlike  spray.  Heavy  drenching  of  the  tree-  al  this  time  should 
be  avoided,  to  guard  as  much  a-  possible  against  the  staining  of  the 
fruit  at  picking  time. 

Approved: 

.1  wil  -    WlL8<  >\. 

s    /■.  fury  of  AgricultuPi . 
Washington.  I>.  C,  February  .'■'.  /!>/>>. 

[Clr.  l 

o 


UNIVERSITY  OF  FLORIDA 

lllffllllllll         III 

"''"l  1262  09216  5116 


